Reciprocating hermetic compressors have their suction provided with an acoustic dampening system (acoustic filters or suction mufflers) provided inside the shell and which conducts the gas coming from the suction line to the suction valve.
This component executes several functions that are important to the adequate operation of the compressor, such as gas conduction, acoustic dampening and, in some cases, thermal insulation of the gas that is drawn to the inside of the cylinder.
The suction muffler generally consists of a sequence of volumes and tubes that conduct the gas coming from the suction line directly to the suction valve. This gas displacement produces pulses, generating noises that are propagated in an opposite direction to the gas flow toward the suction valve. The more efficient the suction muffler at its acoustic outlet, the lower will be said pulses.
Another important function of the suction muffler is to conduct the gas to the suction valve with the least possible heating, avoiding thermal exchanges with the gas stagnated inside the compressor shell and also reducing its contact with the hot parts inside the compressor. On the other hand, the suction muffler represents a load loss to the gas flow being drained. Its influence on the performance of the compressor is highly important. The suction mufflers are mostly constructed in a material of low thermal conductivity and affixed to the compressor head through the cylinder cover. The dimensioning of the internal volumes of the suction muffler tubes determines, to a great extent, the efficiency of the latter.
In some known constructions for the compressors of refrigeration systems, the gas suction occurs by direct suction from the inlet tube to the inside of the suction muffler. In these constructions, the suction line is maintained in fluid communication with the suction muffler through a flexible connector that conducts the cold suction gas directly to the interior of the muffler, minimizing the thermal exchanges of this cold gas with the gas stagnated inside the shell. This connection can be constructed in a flexible material of low thermal conductivity and retained to the suction muffler and in a sliding contact with the compressor shell, such as it occurs in the solution described in U.S. Pat. No. 4,793,775.
In this type of prior art construction, the flexible connector works adequately during the normal operation of the compressor, directing the cold gas from the suction line to the suction valve, without submitting this incoming gas flow to be mixed with the heated gas contained in the compressor shell, and also minimizing the transfer, to the shell, of the noises resulting from the gas pulses inside the suction muffler.
However, this known construction presents the inconvenience of not allowing the refrigeration system to rapidly and adequately return to the pressure levels of the normal working regimen of the compressor, when the latter is driven after a stop period in which the pressure inside the shell is raised to a value of equilibrium with the suction and discharge sides of the compressor.
When the compressor is re-started, the pressure inside the suction muffler and inside the flexible connector is suddenly reduced, originating a pressure differential that is greater than the stop pressure inside the compressor shell, causing a certain collapse of the flexible connector and the compressor assembly tilts toward the shell, compressing the flexible connector and submitting it to undesirable efforts as long as the strong pressure unbalance condition lasts between the interior of the shell and the interior of the suction muffler. Since the latter is constructed, in case of the direct suction, to be relatively hermetically coupled to the inlet of the suction muffler and to the shell, the pressure inside the latter remains high in relation to the interior of the suction muffler for a long period, during which the flexible connector remains resiliently deformed and inadequately subjected to undesirable efforts that tend to damage it or displace it from its operative position.